Bacterial diversity in the gut plays an important role in human health… but the critical question is where the sources of this diversity are located. Because if it is established that a significant part of the maternal microbiota is transferred to the baby at birth, and that the same thing happens during the breastfeeding period via breast milk, other sources still remain to be discovered. There is food of course, but what exactly? Today, scientific consensus believes that certain dietary components beneficially modulate the intestinal microbiota: fermented foods containing probiotics, fiber, prebiotics, resistant starch and fruits and vegetables. For the latter, the hypothesis is that their richness in polyphenols and fiber contributes to transforming the intestinal microbiota into a profile more favorable to health by increasing the presence of “good” bacteria (lactobacilli, bifidobacteria, etc.). This would now be proven in the light of the conclusions of a study published in Gut Microbesproviding evidence of a link between plants and the human intestinal microbiota.
Specifically, the study by researchers at Graz University of Technology demonstrates that the regularity with which a host eats fruits and vegetables influences the amount of bacteria in the gut. Early childhood, in particular, represents a window of opportunity for colonization by plant-associated bacteria. As a reminder, a microbiota is the set of all the microorganisms that colonize a macro-organism (human, animal, plant) or a part of it, for example the intestine or a fruit. While individual microbiota are increasingly understood, scientists know little about their connections. “Evidence that microorganisms from fruits and vegetables can colonize the human gut has been established for the first time. “, explains the first author of the study Wisnu Adi Wicaksono. “ This suggests that their consumption, especially during early childhood, has a positive influence on the development of the immune system during the first three years of life, as the gut microbiota develops during this period. »
Feed the right populations of bacteria
But even after this period the scientific team affirms that maintaining a good diversity with regard to these “good” intestinal bacteria strengthens the resilience of the body throughout life. “ Diversity influences the resilience of the organism as a whole; greater diversity translates into greater resilience. », adds the expert. But how can we explain this beneficial link? The latter explains in Nutrition Insightthat certain bacterial genes present in fresh produce are important for human health, because they are involved in the production of vitamin B12 and short-chain fatty acids. The former acts as a cofactor, contributing to multiple metabolic pathways in humans, while the latter may help improve intestinal barrier integrity and regulate the immune system. To be able to determine that the consumption of fruits and vegetables and their microbiomes indeed leads to changes in the gut microbiome, the team first created a data catalog on the microbiome of fruits and vegetables.
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This involved reconstructing representative genomes of bacteria associated with fruits and vegetables from 156 fruit and vegetable metagenomes before using these reconstructed genomes to study the prevalence of associated bacteria in nearly 2,500 intestinal metagenomes accessible to the audience. The researchers found that bacterial genes involved in the production of vitamin B12 (also called cobalamin) and short-chain fatty acids were consistently present in the human gut, albeit at low levels (about 2.2 percent). ). This amount was influenced by the person's age, the frequency with which they ate vegetables, and the diversity of their plant consumption. Faced with this discovery, microbiology attests that “ fresh produce, including its microbiome, has the potential to influence the composition of the gut microbiome. By identifying personalized diets that can alter the microbiome or metabolites produced by the microbiome, we may be able to prevent or control the consequences of disease. »
“Each fruit and vegetable has a unique microbiota”
To further this research as part of the EU-funded Hedimed project, the scientific team has already started work on an intervention study in which people from three continents eat the same foods over a period of time. given and, following which their stools are analyzed. “ Depending on the results of the planned study, there could also be interesting applications for individuals. Each fruit and vegetable has a unique microbiota. So perhaps at some point a personalized diet can be developed based on this. ”, she notes. Added to this is the fact that this evidence constitutes a crucial element in proving the WHO's One Health concept, which is based on a simple principle, according to which the protection of human health involves that of animals. and their interactions with the environment. Because of this link, practices such as agriculture, animal husbandry, and post-harvest treatments that affect these microorganisms could also directly or indirectly affect the composition of microorganisms in the gut.
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In other words, soil, fertilizers and pesticides affect the microbiota of plants, a phenomenon which can also impact the microbiota of the people who consume them. “ Fresh fruits and vegetables will always have the best microbiome. Agricultural or processing companies already have a major influence here and food storage and processing also need to be critically reconsidered. », conclude the researchers. There is therefore food for thought, given that human activities have already been linked to changes in the diversity of microorganisms found in plants, changes which ultimately impact our health. Note that Inserm indicates that there are different microbiota in the body: in the skin, mouth, vagina, lungs, etc. But the intestinal microbiota turns out to be the most “populated” by between them, harboring at least 10 microorganisms. It is mainly located in the small intestine and the colon, distributed between the lumen of the digestive tract and the protective biofilm formed by the intestinal mucus which covers its interior wall.